[CVE-2022-32224] Possible RCE escalation bug with Serialized Columns in Active Record

Security Announcements
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There is a possible escalation to RCE when using YAML serialized columns in Active Record. This vulnerability has been assigned the CVE identifier CVE-2022-32224.

Versions Affected: All. Not affected: None Fixed Versions: 7.0.3.1, 6.1.6.1, 6.0.5.1, 5.2.8.1

Impact

When serialized columns that use YAML (the default) are deserialized, Rails uses YAML.unsafe_load to convert the YAML data in to Ruby objects. If an attacker can manipulate data in the database (via means like SQL injection), then it may be possible for the attacker to escalate to an RCE.

Impacted Active Record models will look something like this:

class User < ApplicationRecord
  serialize :options       # Vulnerable: Uses YAML for serialization
  serialize :values, Array # Vulnerable: Uses YAML for serialization
  serialize :values, JSON  # Not vulnerable
end

All users running an affected release should either upgrade or use one of the workarounds immediately.

Releases

The FIXED releases are available at the normal locations.

The released versions change the default YAML deserializer to use YAML.safe_load, which prevents deserialization of possibly dangerous objects. This may introduce backwards compatibility issues with existing data.

In order to cope with that situation, the released version also contains two new Active Record configuration options. The configuration options are as follows:

  • config.active_record.use_yaml_unsafe_load

When set to true, this configuration option tells Rails to use the old “unsafe” YAML loading strategy, maintaining the existing behavior but leaving the possible escalation vulnerability in place. Setting this option to true is not recommended, but can aid in upgrading.

  • config.active_record.yaml_column_permitted_classes

The “safe YAML” loading method does not allow all classes to be deserialized by default. This option allows you to specify classes deemed “safe” in your application. For example, if your application uses Symbol and Time in serialized data, you can add Symbol and Time to the allowed list as follows:

config.active_record.yaml_column_permitted_classes = [Symbol, Date, Time]

Workarounds

There are no feasible workarounds for this issue, but other coders (such as JSON) are not impacted.

Patches

To aid users who aren’t able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.

  • 7-0-yaml_safe_load.patch - Patch for 7.0 series
  • 6-1-yaml_safe_load.patch - Patch for 6.1 series
  • 6-0-yaml_safe_load.patch - Patch for 6.0 series
  • 5-2-yaml_safe_load.patch - Patch for 5.2 series

Please note that only the 7.0.Z and 6.1.Z are supported at present. 6.0.Z is supported only for severe security issues. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.

A patch and release are available for 5.2.Z, though it is no longer supported.

Credits

Thanks to @elebow for reporting this! HackerOne 5-2-yaml_safe_load.patch (21.3 KB) 6-0-yaml_safe_load.patch (24.2 KB) 6-1-yaml_safe_load.patch (25.6 KB) 7-0-yaml_safe_load.patch (29.3 KB)

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